Former Vermont Governor and Democratic National Committee Chair Howard Dean has long supported IRV.

Excerpt from Dean's book What We Do Now:

One of the first issues we need to address if we’re going to get
out the vote at a level required by a truly participatory democracy is
the lack of excitement many people feel for the candidates put forth by
our parties.

Right now, in primaries, and in general elections where there’s a
third-party candidate, a fair number of voters feel forced to choose
the candidate they think is viable. In the end, if they really want to
defeat the opposition, they choose the candidate they think is most
likely to do so, without enthusiasm and without much pride. As they
often put it, they feel as if they’re choosing the lesser of two evils.
A population that feels like this is not going to be very motivated to
vote.

One way to overcome this problem is by changing our voting system
so that people can vote for candidates they believe in without risking
the kind of outcome we saw in 2000 when third-party candidate Ralph
Nader drew enough votes from Al Gore to ensure President Bush’s
Electoral College win. Other countries do this through a multi-party
system that rules by coalition. We can do it in America by bringing in
a new voting system that allows coalitions to be built as you vote.
It’s called instant runoff voting.

Instant runoff voting is a system in which you vote by ranking two
or three candidates in order of preference. When the votes are tallied,
if your top choice gets knocked out of the running, your vote reverts
to your number two, and so on. It’s like having a runoff election, only
you don’t need two elections to do it. This system, which has attracted
the interest of a number of reform-minded people around the United
States, is already in use in Europe and in city council elections in
Cambridge, Massachusetts. Instant runoff voting was successful in San
Francisco on Nov. 2. Although there were some minor glitches, I suspect
they will keep using it.

By way of illustration: Had we used instant runoff voting in 2000,
most Nader supporters would have gone to the polls and voted for Ralph
Nader first and Al Gore second. Since Nader, in the three-way tally
afterward, wouldn’t have finished in one of the top two slots, Al Gore
would have been the beneficiary of roughly 60 percent of his votes and
would have been chosen as the next president of the United States.
(Most of Pat Buchanan’s votes most likely would have gone to President
Bush.)

Instant runoff voting would be beneficial for our electoral
process, because it would encourage candidates to hold a firm set of
principles without worrying that their beliefs could make them
unviable. It would allow people to vote for candidates they really want
to elect, thereby increasing both enthusiasm and turnout.

Comment on "NewsNight," CNN, November 12, 2003:

If I could do anything I wanted and have campaign
finance reform, here's what I would do. I would have small donations
allowed, $100 or less. I would have public financing of everybody's
campaign. And I would limit people's spending, so nobody could go
outside the public financing system. And I would have instant
run-off voting, so, when you had more candidates than just two, the
person with a majority of votes would win. Now, that's what I would
like to do. I believe in campaign finance reform. But I don't
believe in campaign finance reform that gives a significant
advantage to the Republican Party. And that's what we have now.

Howard Dean frequently mentions IRV when asked
about campaign finance reform. For example,
at the Linn County Iowa Democratic Fundraising Dinner on January 18,
2003 that was carried on
CSPAN, Dean said:

If you want real campaign finance reform,
here's what you've got to do, and you have to do all three at once.
You have to do public financing of campaigns, you have to have
instant runoff voting, so Ralph Nader doesn't take the election away
from Al Gore, although we know it was really the Supreme Court that
did that, and you've got to have either a constitutional amendment
or a better court that will say free speech and political
contributions are not the same thing. We can do better than the FEC
is doing right now, which is busy gutting McCain/Feingold, which a
lot of people right here worked very hard for.